Carboxypeptidase U at the interface between coagulation and fibrinolysis

In 1988, Hendricks et al. first reported on the presence of carboxypeptidas e U (U refers to the unstable nature of the enzyme) in human serum. One dec ade later, the importance of carboxypeptidase U (CPU) in the regulation of fibrin clot dissolution is well documented. CPU circulates in plasma as an inactive zymogen, proCPU, that is converted to its active form during coagu lation and fibrinolysis. CPU cleaves off C-terminal lysine residues exposed on fibrin partially degraded by the action of plasmin. Because these C-ter minal lysine residues are important for upregulating the fibrinolytic rate, CPU thus slows down fibrinolysis.